Lung diffusion: how is the capacity of the lungs tested?

A pulmonary or lung diffusion is a diagnostic test that measures how well the lungs are working by comparing the amount of carbon monoxide in the air you breathe out with the amount in the air that you breathe in. This tests the amount of oxygen being absorbed in the blood.

What is pulmonary testing?

This pulmonary test determines the degree of efficiency with which oxygen crosses the alveolar walls and is transferred from the lungs to the blood.

The pulmonary capillary bed is a very fine barrier connected to the alveoli of the lungs and functions as a filter for the blood. In normal circumstances, there should be no problems in this gaseous exchange: the oxygen (O2) of the inhaled air is absorbed well and passes into the blood, while the carbon dioxide (CO2) passes from the blood to the alveoli to be exhaled.

Generally speaking, if this does not occur efficiently and oxygen exchange between the lungs and blood is abnormal, it may be a symptom of serious diseases such as pulmonary fibrosis, pulmonary embolism, hypertension, asthma, emphysema, or other pulmonary blood vessel problems.

How does the pulmonary function test work?

The pulmonary diffusion test should be performed by highly qualified specialists in the field of pulmonology, as specially designed equipment is needed.

The pulmonary diffusion test is not only useful for detecting problems, but can also be used for monitoring and evaluating the progression of a disease.

Before proceeding with the examination, it is very important to know the patient's basic data (sex, age, height, weight). It is also essential to know the levels of haemoglobin in the blood of the patient, as in some cases such as patients with anaemia, the values of the diffusion test are affected.

How long does a lung capacity test take?

In general, the test lasts between five to ten minutes, and involves the patient wearing a tight-fitting mouthpiece and a nose clip. The patient inhales a mixture of gases with a small concentration of carbon monoxide, holding their breath for ten seconds and then expels the air, enabling the medical team to analyse and measure the difference in the concentration of inhaled and exhaled gases.

Why have a lung capacity test?

The test is useful for the diagnosis and treatment of pulmonary emphysema (COPD), a disease that can develop in smokers. Respiratory consultants recommend lung screening for all smokers over 35 years of age who have smoked an average of one pack per day over the last ten years. It is also advised in cases of interstitial diseases, lung diseases and in the assessment of surgical risk in cases of lung surgery.

The pulmonary diffusion test is very useful for diagnosing certain lung diseases and for monitoring the condition of people with established lung disease. It is simple and easy to perform and has no side effects.

Once the problem is detected, the treatment of the disease in question can begin.